Gautam Gowrisankaran

A Dynamic Model of Endogenous Horizonal Mergers

I develop a dynamic model of mergers, where mergers, investment, entry, and exit are endogenous variables rationally chosen by firms to maximize expected future profits. This model differs from previous analyses in that it incorporates dynamics and endogenizes the merger process. The model generates reasonable predictions: allowing for mergers has the expected effect on entry, exit, investment, and surpluses; changes in tastes and technologies affect industry equilibrium in plausible ways. The results demonstrate that this type of analysis is feasible and can potentially be used as a tool for antitrust policy analysis.

Estimating the Quality of Care in Hospitals Using Instrumental Variables

Mortality rates are a widely used measure of hospital quality. A central problem with this measure is selection bias: simply put, severely ill patients may choose high quality hospitals. We control for severity of illness with an instrumental variables (IV) framework using geographic location data. We use IV to examine the quality of pneumonia care in Southern California from 1989 to 1994. We find that the IV quality estimates are markedly different from traditional GLS estimates, and that IV reveals different determinants of quality. Econometric tests suggest that the IV model is appropriately specified, that the GLS model is inconsistent.

Dynamics of Consumer Demand for New Durable Goods

Most new consumer durable goods experience rapid prices declines and quality improvements, suggesting the importance of modeling dynamics. This paper specifies a dynamic model of consumer preferences for new durable goods with persistently heterogeneous consumer tastes, rational expectations, and repeat purchases over time. We estimate the model on the digital camcorder industry using panel data on prices, sales, and characteristics. We find that the 1-year elasticity in response to a transitory industrywide price shock is about 25 percent less than the 1-month elasticity. Standard cost-of-living indices overstate welfare gain in later periods due to a changing composition of buyers.

Mergers and the evolution of industry concentration: results from the dominant- firm model

To what extent will an industry in which mergers are feasible tend toward monopoly? We analyze this question using a dynamic dominant-firm model with rational agents, endogenous mergers, and constant returns to scale production. We find that long-run industry concentration depends upon the initial concentration. A monopolistic industry will remain monopolized and a perfectly competitive industry will remain perfectly competitive. For intermediate concentration levels, the dominant firm may acquire or sell capital, depending on its ability to commit to future behavior. Industry evolution also depends on the elasticities of demand and supply and the discount factor.

Quantifying Equilibrium Network Externalities in the ACH Banking Industry

We seek to estimate the causes and magnitudes of network externalities for the automated clearinghouse (ACH) electronic payments system, using a panel data set on individual bank usage of ACH. We construct an equilibrium model of consumer and bank adoption of ACH in the presence of a network. The model identifies network externalities from correlations of changes in usage levels for banks within a network, from changes in usage following changes in market concentration or sizes of competitors and from adoption decisions of banks outside the network with small branches in the network, and can separately identify consumer and bank network effects. We structurally estimate the parameters of the model by matching equilibrium behavior to the data, using simulated maximum likelihood and a data set of localized networks, and use a bootstrap to recover confidence intervals. The parameters are estimated with high precision and fit various moments of the data reasonably well. We find that most of the impediment to ACH adoption is due to large consumer fixed costs of adoption. The deadweight loss from the network externality is moderate: the optimal number of ACH transactions is about 16% higher than the equilibrium level.

Learning and the Value of Information: The Case of Health Plan Report Cards

We estimate a Bayesian learning model in order to assess the value of health plan performance information and the extent to which the explicit provision of information about product quality alters consumer behavior. We take advantage of a natural experiment in which health plan performance information for HMOs was released to employees of a Fortune 50 company for the first time. Our empirical work indicates that the release of information had a small but statistically significant effect on health plan choices, causing 3.1% of employees to switch health plans. Although consumers were willing to pay an extra

Efficient representation of state spaces for some dynamic models

267 per year per below average rating avoided, the average value of the information per employee was only

The Welfare Consequences of ATM Surcharges: Evidence from a Structural Entry Model

10 per year. The relatively small impact of the ratings arises because the ratings were estimated to be very imprecise measures of quality. More precise measures of quality could have been more valuable.

Managed care, drug benefits and mortality: An analysis of the elderly

Many important economic problems require computation over state spaces that are not hypercubes. Examples include industry models of multi-product differentiated product firms, Bayesian learning problems with noisy signals and real business cycle models with heterogeneous agents. These problems have not been analyzed partly because of the difficulty in efficiently representing their state spaces on a computer. I develop a representation algorithm for the state spaces of the above problems, which potentially allows them to be solved with computational methods such as dynamic programming. I find that using this representation reduces the computation time and space by several orders of magnitude relative to a naive representation.

Measuring Network Effects in a Dynamic Environment

We estimate a structural model of the market for automatic teller machines (ATMs) in order to evaluate the implications of regulating ATM surcharges on ATM entry and consumer and producer surplus. We estimate the model using data on firm and consumer locations, and identify the parameters of the model by exploiting a source of local quasi-experimental variation, that the state of Iowa banned ATM surcharges during our sample period while the state of Minnesota did not. We develop new econometric methods that allow us to estimate the parameters of equilibrium models without computing equilibria. Monte Carlo evidence shows that the estimator performs well. We find that a ban on ATM surcharges reduces ATM entry by about 12 percent, increases consumer welfare by about 35 percent and lowers producer profits by about 20 percent. Total welfare remains about the same under regimes that permit or prohibit ATM surcharges and is about 17 percent lower than the surplus maximizing level. This paper can help shed light on the theoretically ambiguous implications of free entry on consumer and producer welfare for differentiated products industries in general and ATMs in particular.